Last week-end, I attended the Alchimie demoparty with my wife. As usual, it was a pretty cool event.
I made a small conference about logic analyzer, introducing the SUMP Logic Analyzer project and performing a small study of the Amiga 500 internals. You can find the slides here.
Some pictures of the event :

Everything you need to know about the Guimauve 2ooo Apple //c VGA adapter can be found here : http://silicium.org/g2k/.
Last details have been sorted out, and boards are now available for purchase.
Enjoy!

Last week-end, it was the VieuMikro retrocomputing meeting. IMO, this year's issue was the best I ever attended : we did put some effort into the organization, which was appreciated by people.

I brought my X68000 Expert, a machine that is always appreciated, and spent some time trying to have a rare Tangerine Microtan 65 computer work (an half-success, as we managed to have it display a random set of well-formed characters, so it looks much like a simple RAM issue).


(picture courtesy of Jeremie Marsin)

I also made a presentation of the Guimauve 2ooo project. For those who are interested in getting such a board, a dedicated web page will soon be online, with all the project details, and ordering info.

After many tedious hours of soldering, here are the 8 first Guimauve 2ooo Apple //c VGA adapters :



More to come soon, after the official announcement that will occur during VieuMikro event.

Some time ago, I managed to get a (broken) X68000. The power supply died the first time I powered it on, but it wasn't much of an issue, as you can easily replace a broken power supply with a standard ATX one, as explained here.

The main issue with this X68000 was an overclocking mod that had been performed by its previous owner, and prevented the machine to boot. I managed to remove this mod (the tricky part was to eventually find a track on the motherboard, which had been cut), and everything went fine. However, having an ugly grey box (the only spare ATX power supply I had at that time) was really awful, especially as I love the case design of this machine.
So I purchased another ATX power supply, and managed to fit it into the case, reusing the original fan for proper cooling of the whole thing.
Here is a picture of the X68000 and its brand new power supply ;)

Exelvision is an obscure brand of computers from France, that operated in the 80s, their most famous home computer being the Exl 100.
For more information, here is Fabrice Montupet's Exelvision-related website, which is the largest source of information you can find on this company and their computers.

The Exl 100 embeds two CPUs : a TMS7020, and a TMS7041, the TMS7020 being the main CPU, whereas the 7041 is used as a microcontroller, and is responsible for most I/O related stuff, including screen display (for instance, it stores in its internal ROM the character table).
Until now, the contents of this ROM hadn't be retreived, so it was an issue for emulator writers. However, someone on Silicium's forum found this newsgroup thread, explaining a way to retreive the internal ROM contents of a PIC7040, which is very close to the TMS7041, so I decided to give it a try.
For this purpose, I used my favorite FPGA board, to make the TMS7041 output its internal ROM to the board's SRAM, then dump the SRAM contents over a serial port. Here is a picture of the whole stuff :



After some attempts, it seems that it worked fine :) Emulator writers are currently analyzing the ROM contents, and have a good feeling about it.
It should hopefully lead to a better understanding and emulation of these obscure machines.

This year, Infoticaires event was nice, as usual. The main noticeable difference was that it was much more console-oriented than computer-oriented.
There was also a band playing covers of videogame music themes, which was pretty nice.
As I'm not much into gaming (at least, currently), I spent much of my time working on fixing the color scheme of the Guimuave 2ooo adapter.



You can read a detailed report (in French) here.

I fixed the mistakes I made on the previous prototype, and I managed to add a small feature : it is now possible with the help of a jumper to choose between color mode, or green-and-black monochrome mode, for those who (like me) had a monochrome display, and prefer to use this mode which provides a crisper picture.

Here is a picture of the final PCB, assembled.



I still need to tweak the CPLD code a bit, but it should be now only a matter of weeks until first boards are available for those who might be interested. I'll tell more about it later.

The Chat-Mauve-clone-but-with-VGA-output needed a name, and here it is : "Guimauve 2ooo".
Here are some pictures of the first prototype, which works fine !





You may wonder what happened to what should have been a nice board ? ;) Well, I made two stupid mistakes so I add to cope with them :

• The part I selected in Eagle as the DB-15 connector on the Apple side had its pin numbering "reversed".
  
• I totally "forgot" that one of the components expected a 5V power supply, while all the others use 3.3V, so I added it.
  
  

I will have to redesign the board but well, it won't be much of a big deal.

I just finished designing the board, using parts I already own for the most :



It has been designed to be the more "homebrew-compliant" possible : it is single-sided, and there will be only a single wire to add. Next step, order parts, and build the PCB (or have it manufactured), then hope the whole thing will work ;)

Here is a new picture, with VGA colors fixed. I still use a 2-bits R-2R ladder for output, so the colors are still a bit different from what's produced by the original adapter, but I can't say that the result is better or worse, so I'll probably keep it this way.
On the left, the original adapter's output on a LCD TV, on the right, VGA output of my adapter.



The image isn't very crisp (I get a better image using Starter Board's own VGA output, even if it only features 1 bit per component). It means that it's now the time to make a proper board, instead of having such a mess of wires hanging around ;)
The desing still uses less than 60 macrocells, so it could fit into a XC9572XL for instance, which is probably what I'm gonna use at the end.

I managed to modify the VGA adapter of the Apple II+ on a FPGA to meet the requirements of my previous post.
It stills runs off the FPGA but, it uses the board's SRAM instead of internal block ram. The design fits well in a XC9572 CPLD, which is quite fine.


Colors are still a bit off, but text display works nice, showing that interleaved SRAM access works. Now I need to fix the colors (shouldn't be much of a big deal, as I already solved the issue on the SCART version), then use a CPLD, to be as close as possible of what would become a final version ;)

My "Chat Mauve" video adapter clone is now working, at least for a basic rendering.
Let's start with a picture of my mess :



On the main TV you can see it running. On the secondary TV, you can see the monochrome NTSC output provided by the Apple //c.
My design is currently running on the FPGA board, but is simple enough to run off a small CPLD. I just wanted to keep all my logic analyzer stuff in place to do some tweaking. For now, I just use a 2-bit R/2R ladder for each R,G,B output, and the screen rendering displays an horizontal resolution of 140 (instead of 280 for a HiRes screen), as my primary goal was to test the full range of colors available.

Here you can see a picture of the original Chat Mauve adapter rendering (displaying Little Computer People, a really nice game, let's call it the grandfather of the Sims) :



Now a picture of the same game, using my adapter :



As you can see, the colors are a bit different, and you can see the effects of the "half-resolution" screen rendering. Well, apart from the screen rendering, which can be probably easily fixed, the result is quite nice. I might test a 3-bit R/2R ladder if if want to get closer to the actual color display but it already looks nice.

Another thing that camed to my mind when I started this project was to make a VGA output, instead of a simple clone of the current adapter. During my quest for information on Internet, I found this project : Apple II+ on a FPGA.
It contains almost everything I need, as it can output video to a VGA screen. The 0.1 version of this project is pretty close to what I've found so far by analysis (and it also provides a 140 pixels wide rendering). The 1.0 version provides an interesting color-generation scheme, which looks pretty tricky to me, with my current knowledge of the Apple video generation internals.

I'm sure this project will be helpful, but for the VGA rendering, I will need to rework some parts, as :

• The 1.0 version of the VGA display uses a 28Mhz clock, instead of the 14Mhz clock provided on the video connector.
  
• It uses a dual-port internal BlockRAM, where I plan to use (whenever possible) a single port SRAM. Dual-port RAM is quite expensive, so I'd rather use standard single-port RAM (and it will make the (hopefully) upcoming board easier to route).
  
• It also relies on vertical and horizontal blank, whereas the video connector only provides composite blank.
  
  

Well, it's already a first major step for my project, but there's much more to come... Stay tuned ;)

It's been some time now since my last site update, mostly because of my lack of time...
Anyway, back to "work" with a new project : design a "Chat Mauve" video adapter clone at first, then maybe an enhanced version. The "Chat Mauve" adapter was designed to provide a RGB output on a SCART connector, for Apple //c computers. At Silicium, despite owning many Apple //c units, we've been able to find only one of those adapters so far, hence this idea of making a clone.
The adapter comes in a very small beige box. I opened it, expecting to find only a couple of passive components or simple logic chips in so few space, and I found myself quite surprised, as the box contains only a single custom chip (along with its voltage regulator) !
As expected, I didn't find anything useful on the web, so I searched for some information about the Apple //c video output and Apple II computers hardware. After some reading, it seems that making a RGB output out of the video signals provided isn't a trivial task, but doesn't seem too hard either.

Then I remembered a nice project I found on the web some time ago : the SUMP Logic Analyzer. It's an open-source FPGA-based logic analyser, with a client software in Java. It uses the Spartan-3 Starter Board as a primary target, which is fine, as I own one of those. So I decided to give it a try, as it should fit nicely for the project's purpose.

First step : put all the adapter's connector signals on a breadboard, and see which ones are used by the custom chip.



No big suprise here, almost all of them are used... Second step, set up the logic analyzer...



... and start analyzing, which is what I'm about to do now. I spent some time these last days to add a VHDL export to the SUMP Logic Analyzer Client, so I could use analyzer results as testbenchs for the upcoming design. On a side note, I'm using my Samsung NC10 "netbook" to run the logic analyzer client... Who said that netbooks are only suitable for basic tasks ? ;)

Last week-end, I attended the Toulouse Game Show, which is in my guess, the biggest geek convention close to Toulouse. You could find all kind of stuff, including (but not limited to) anime, manga, cosplay, hentai, arcade, rhythm games, import shops, star wars geeks, guest stars. It was very cool indeed. The Silicium association prepared a Famicom-related expo for the event.


See my Picasa photo album : Toulouse Game Show 2oo8